As you say I don't think I'll win any records for coldest. I think my coldest brew day was -17C/1F (-33C/-27F with windchill). That's not even considered cold in some parts of Canada and the US.I don't know if he takes the record for coldest brew day, but I am sure that Bradsul is up there for the most brews in the bitter cold.
See his pics (and cold weather equipment mods):
https://www.homebrewtalk.com/f11/winter-brewing-outdoors-47031/